Debarker



April 6, 1965 s. BROADBENT 3,176,734

DEBARKER Filed Sept. 2'7, 1962 7 Sheets-Sheet 1 INVENTOR J'TANLfY BROADBfNT ATTORNEY April 6, 1965 s. BROADBENT 3,176,734

DEBARKER Filed Sept. 2'7, 1962 7 Sheets-Sheet 2 g; INVENTOR su/vm BRO/101ml ATTORNEY April 6, 1965 s. BROADBENT 3,176,734

DEBARKER Filed Sept. 27, 1962 7 Sheets-Sheet 5 ATTORNEY April 6, 1965 Filed Sept. 2'7, 1962 S. BROADBENT DEBARKER '7 Sheets-Sheet 4 INVENTOR April 1965 s. BROADBENT 3,176,734

DEBARKER Filed Sept. 27, 1962 '7 Sheets-Sheet 5 INVENTOR STA NLE Y BAOADEfA/T ATTORNEY APrll 1965 s. BROADBENT 3,176,734

DEBARKER Filed Sept. 27, 1962 7 Sheets-Sheet 7 ATTORNEY INVENTOR STANLEY B ROA DBEN T 3,176,734 DEBARKER Stanley Broarlbent, Box 164-, Quincy, Pa. Filed Sept. 27,1962, Ser. No. 226,638 7 Claims. Cl. l te-4%) This invention relates to the utilization of timber to produce lumber, slabwood, chips and the like for subsequent uses in various ways including in the production of paper and other products.

The invention relates particularly to the removing of bark from logs without injuryto the logs whereby maximum utilization can be had of the slabwood, chips and other components and relates additionally to apparatus and equipment by which such results may be accomplished.

Logsof various kinds have widely different bark characteristics including thickness, texture, nature and degree of adhesion between the bark and the underlying wood, as well as temperatures of the logs, all of which present a problem in the treatment of the logs to remove the bark without injuring or impairing the equality of the underly ing woodfiber.

In the production of lumber with fiat surfaces from logs having round exteriors there, are left slabs and chips, the most appropriate use of which is for pulp in themanufacture of paper products, and inorder to obtain an end product of the best quality the complete removal of the bark without damage to the underlying wood is essential and presents a distinct problem.

It is an object of the invention to provide a machine or apparatus which will readily, expeditiously, and etficiently remove bark from logs having the various characteristics indicated without causing damage to the underlying wood fiber and thereby making available maximum usable material of the highest quality commensurate with the initial composition of the log.

Another object of the invention is to provide a machine or apparatus for removing barkfrom logs of the various characteristics, including improved control of the pressure, penetration, and speed of the cutting mechanism as well as the rotational speed of the logs, and with all of such control features subject to the will of the operator duringthe operation of the machine in the removal of the bark.

Another object of the invention is to provide a machine for removing bark from logs inwhich a portion of the pressure applied to the cutting mechanism is by positive pressure hydraulic or otherwise with a compensating reaction by a compressible medium of a gaseous character.

Another object of the invention is to provide a log debarker having a cutter head which can travel in either direction along the length of the log, which can be set according to the thickness of the bark to be removed, with the cutter head carried on a floating boom pivoted initially about a cross rod at one end 'and sequentially pivoted about a second cross rod approximately midway its ength for proper balance, the initial pivot point being hydraulically supported by means of a yieldable medium such as a gas cylinder piston or other yieldable substance with such gas inert to temperature where low temperatures prevail and such gas cylinder exerting a predetermined constant force on the free end of such boom when the boom is pivoted about the second pivot.

A further object of the invention is to provide a log debarker including an arrangement of balanced boom, linkages, slides, and cushion cylinders for obtaining any desired cut or pressure on the log within close limits, and for maintaining pressure during variations of the character of the logs surface. and of a capacity to rapidly repeat or change these conditions to obtain optimum knife pressure for various log characteristics.

Other objects and advantages of the invention will be United States Patent apparent from the following description taken in conjunction with the accompanying drawings wherein:

PEG. 1 is a perspective illustrating one application of the invention;

FIG. 2, a top plan view;

FIG, 3, a section on the line 3--3 of FIG. 2 disclosing the debarker carriage in elevation;

FIG. 4, a transverse section on the line ld ot'PlG. 2;

FIGS. 5 and 6, sections respectively on the lines 5--5 and 5 -5 of FIG. 3; 7

FIG. 7, a horizontal plan view with the top one of the guide channels removed;

8, a vertical section on the line 3-8 of FIG. 7;

IG. 9, a horizontal section on the line 9-9 of FIG. 7;

FIG. 10, a front elevational view on the line 1tllli of FIG. 3;

FIG. 11, a horizontal section along the line 11l1 of FIG. 10;

PEG. 12, a fragmentary section on the line 12-43 of PEG. 2;

FIG. l3, a schematic view of the wiringdiagram; and

FIG. 14, a diagrammatic view of the hydraulic system.

Briefly stated, the traveling head debarker of the present invention includes a frame with mechanism thereon for supporting and rotating the logs while reciprocating cutter means moves lengthwise of the log to enable the cutters to engage and remove the bark. ivlea-ns is provided whereby the depth of cut may be set according to the thickness of the bark to be removed and. additional means is provided for controlling the rotational speed of the log, the pressure, penetration, and travel of the cutters all subject to the will of the operator during the removal of the bark. The pressure advancing of the cutting mechanism into the bark of the log is by positive non-compressible iluidaction with a compensating reaction subjectlto a compressible gas.

The cutting head is constructed for travel in either diplate of rection along the length of the log being debarked, such cuttinghead being mounted on a boom pivoted approximately mid-way its length for proper balance with the pivot point supported by fluid pressure and maintained at the proper elevation of the boom and the rear end of the boom is restrained in its raising and lowering motion by compensating means of a yieldable medium such as a compressible fluid pressure cylinder preferably utilizing a gas inert to temperature where low temperatures prevail. The arrangement of balanced boom, linkage, slides and cushion cylinders are such that any desired cut or pressure on the log withinclose limits can be accomplished as well as a pressure maintained during variations in the diameter of the log and character of the logs bark and of a capacity rapidly to repeat or change these conditions to obtain optimum knife, pressureior various log character istics. i i i The apparatus or machine. for removing the bark from logs includes a drive unit, a cutter head, a balanced beam supporting the drive unit and cutter head,.a second beam, toggle linkage connecting the beams and forming a compound lever system capable of moving the axis of the balanced boom in an arc of a given radius around the opposite end of the balanced beam to the cutter head, such arrangement being maintained in a horizontal plane but capable of being displaced vertically with such .displacement Opposed by a pressure cylinder.

With continued reference to the drawings, the debarker of the present invention includes a base or frame lti having a plurality of cross members ll, attached thereto. Spaced hearings or pillow blocks 12 are mounted on each of the cross members 11 and receive generally parallel shafts 13 on which a series of log supporting members such as bull wheels 14 are mounted. These members are adapted to be rotated to impart rotation to a log 15 to be debarked.

In order to rotate the bull wheels, each of the shafts 13 has a sprocket l6 fixed to one end and such sprockets are interconnected by a chain 17 to drive both shafts in the same direction and at the same speed. One of the shafts has a driven sprocket 18 mounted thereon which is connected by a chain 19 to a driving sprocket 20 fixed to the output shaft on a gear reduction 21 driven by a reversible variable speed fluid motor 22. The speed and direction of rotation of the motor 22 are controlled by an operator from a control panel 23 through the medium of a lever 24 which controls a fluid valve 24'.

A secondary frame 25 is connected to the base 10 on one side thereof and such secondary frame is adapted to support a rail or track 26 along the outer edge thereof.

.A second rail or track 27 which is generally angular in cross section is welded or otherwise attached to the side edges of the cross members 11 in spaced relation to the rail 26. The rails 26 and 27 extend substantially beyond the cross members 11 at both ends of the frame for a par pose which will be later described. A carriage 23 is mounted for longitudinal movement along the rails 26 and 27 and such carriage comprises a body 29 of generally inverted U-shaped construction. A pair of spaced wheels 30 are mounted on the outer leg of the carriage body in engagement with the rail 26 and two pairs of spaced wheels 31 are mounted on the inner leg of the carriage body with one wheel of each pair being disposed above the rail 27 and the other wheel of each pair being disposed below such rail. In this manner the inner leg of the carriage is confined both in an upward and a downward direction.

In order to move the carriage 28 in either direction, such carriage is connected to an endless cable 32 which extends over pulley 33 atone end of the base 10 and then bcneath the carriage and around a pulley 34 at the opposite end of the base and back to the carriage. The pulleys 33 and 34 are fixed to shafts 35 and 36 respectively journaled in bearings 37 and 38 to permit rotation of such shafts. The shaft 35 is provided with a driven sprocket 39 connectedby a chain 40 to a driving sprocket 41 mounted on the output shaft of a gear reduction 42 which in turn is driven by a reversible variable speed fluid motor 43 under the influence of the operator through the medium of a lever 44 which controls a fluid valve 44.

A pair of spaced generally parallel upright brackets 43 i are fixed to the upper surface of the carriage 28 and such brackets are adapted to pivotally support a floating heavy wall type boom 49, a compound linkage and mechanism for raising and lowering both ends of the boom sequentially by such compound linkage. In order to do this a pair of elevating beams 50 are pivotally mounted at one end on stub shafts 51 carried by the upright brackets 48. A cross rod 52 connects the intermediate portion of the elevating beams 50 and a cross rod 53 connects the free ends of such beams. A pair of spaced links 54 are pivotally mounted at one end to the cross rod 53 and at the opposite end such links are connected to a cross rod 55 pivotally supported by bearings 56 mounted on brackets 57 which are fixed to the boom 49. The brackets 57 are located approximately midway of the boom to form a fulcrum and the design is such that the boom and its attached equipment is substantially in balance about the cross rod 55. The up and down movement of the elevating beams 50 about the stub shafts 51 is regulated by a hydraulic or other non-compressible fluid cylinder 5 8 having a piston rod 59 the free end of which is fixed to a sleeve 60 disposed about the intermediate cross rod 53. The extension and retraction of the piston rod 5% is caused by the introduction and discharge of a non-compressible fluid into and out of the cylinder 58 through flexible fluid lines 61 and 62 connected to a source of fluid under pressure. The cylinder 58 is controlled by the operator through up and down buttons 63 and M on the control panel 23 which energize solenoids 63' and s4 respectively to operate a fluid valve 58'.

A lower support plate 65 is welded or otherwise attached to the bottom of the boom 49 at one end thereof and a pair of spaced depending bearing blocks 66 are attached to such lower plate by fasteners 67. The bearing blocks 66 rotatably receive a sliding shaft 63 at the outer extremities of which is mounted a slide plate 69. Each of the slide plates 69 is retained between a pair of guide members 7@ fixed to the inner surface of the upright brackets 42; in such a manner that the shaft 63 is guided substantially in a vertical direction. A sleeve 71 is disposed about the shaft 68 intermediate the bearing blocks 66 and such sleeve is fixed to one end of a piston rod 72 received within a gas pressure or cushion cylinder 73 mounted on the carriage 28.

The shaft 68 and the slide plates 69 will be maintained in their uppermost position when the boom 49 is in an inoperative position by the pressure of the compressible gas within the cylinder acting against the piston and piston rod 72. When the cylinder 58 is operated to lower the boom, such boom will pivot about the cross rod 63 until such time as the free end of the boom engages the log. Further downward movement of the piston rod 59 will movethe piston rod 72 downwardly within the cylinder 73 against the pressure of the gas therein. The downward movement of the piston rod 72 continues until one of the slide plates engages a limit switch which stops the flow of fluid to the elevating cylinder 53.

At this point the boom 4-9 is fully floating and is pivotable about the cross rod 55 which functions as a fulcrum. Any up or down movement of the end of the boom will be compensated for by the pressure within the cylinder 73 so that a constant pressure will be applied to the free end of the boom. The guide members 70 are of a length to accommodate any probable movement due to log variations but if the cross rod 68 reaches its lowermost point of travel, a destructive force will be applied to the elevating cylinder 55. To protect against this overload, a relief valve (not shown) may be mounted on the upper portion of the cylinder 58 and set to trip at approximately 1200 psi.

The cushion cylinder 73 employs an inert gas such as dry nitrogen as a protection against freezing when the apparatus is used under subzero conditions. The 'gas is stored in a rechargeable pressure vessel 74 at approximately 2200 psi. and fed through a pressure control valve 75 into an accumulator 76 and such accumulator'is in communication with the cushion cylinder 73 by a flexible line 77. The gas pressure in the accumulator 76 and the cushion cylinder 73 can be regulated to suit the optimum condition for best results, but will usually be in the range of 200-250 p.s.i. The displacement volume of the cushion cylinder is so proportioned with respect to the volume of the accumulator that the force acting against the shaft 68 will not vary more than 3%.

In order to remove the bark from the log, cutting mechanism is provided at the end of the boom remote from the cushion cylinder 73 and such cutting mechanism comprises a head block 80 adapted to be moved along the length of the log by carriage 28 while the log is being roated by the bull wheels 14-. Such head block has a plurality of cutters or knives 81 mounted on each of multiple holders 82 with central hexagonal bores supported by a common arbor or shaft 83. The major portion of the shaft 83 preferable is hexagonal in cross-section for cooperative engagement with the bores of the holders so that such holders 82 may be slidably mounted thereon without the necessity of keys or the like and may be circumferentialiy displaced one sixth of a revolution or 60 around the arbor shaft in a generally spiral arrangement. The arrangement of the cutters and knives is determined by the character and condition of the log to be debarked and if desired the holders 82 may be .to a bracket 99 fixed to 'to and from the cylinder.

mounted on the arbor 83 without the circumferential displacement so that bar knives which span all of the holders may be employed. The cutter and arbor shaft 153 are supported on anti-friction pillow block bearings 84, at tached by bolts 85 to a pairof brackets 36 welded or otherwise fixed to opposite sides of the head block 8h.

The head block 8% is provided with a pair of spaced, curr ed depth gauges or slippers 87 and 855 to which upwardly curved shoes 39 and 911 of cast iron or other suitable material are attached by bolts 91. As the head block moves along the log in either direction one of the shoes will engage the bark and the other shoe will be set at a depth to permit the knives 81 to penetrate the bark to the carnbium layer; In order to do this each of the slippers is mounted at the front or outside end of the headblock Ed by a pivot 92 to a depending lug 93 fixed to the under side of the head block. The free end of each of the slippers is connected by a pivot as to one end of a double ended piston rod 95 having a piston 96 located within an hydraulic cylinder 97. Each of the cylinders is mounted by means of a pivot 18 (FIG. 3) the opposite sides of the head block 80. i

The free end of each of the piston rods $5 extends upwardly out of the cylinder 97 and is slidably received within the sleeve 160 having a substantially vertical slot or opening 1111. Within .thesleeve. 1% the piston rod has a series of rack forming teeth 162 which mesh with a pinion 1113 extending through the opening N1 and carried by a potentiometer 134. The potentiometers are electrically connected to vertically mounted milliammeters 1115 fixed on -the control panel 23 and the pointers or indicators of such milliammeters are displaced by changes in the resistance of the potentiometer 1% to make the exact position of the slippers 8'7 and SS apparent to the operator. The scale of the milliammeter 1115 is calibrated to represent slipper depth and the voltage is stabilized for greater accuracy.

The hydraulic cylinders 9'7 which actuate the slipp rs are independently operable through fluid lines 1116 and 1117 by pressing appropriate up or down buttons 1% and 163, respectively, located on the control panel 23, which energizes one of a pair of solenoids 1111 and 111 of a double solenoid four-way valve 11?. and allows fluid to flow When the button which has been pressed is released the movement of the piston as is stopped and it is effectively locked in position.

The headblock 311 is provided with sleeve bearings 113 attached to each end which ro tatably receive the free end ings 84. Each of such pulleys is driven by a pair of belts 117 which extend around a double pulley 11% mounted on opposite ends of a jack shaft 119 carried 1 by bearings 120 which in turn are fastened by bolts 121 to brackets 122 fixed to opposite sides of the head rality of belts 132 which in turn are driven by a mul tiple sheave pulley 133 fixed on the shaft 134 of a motor 135. The motor 135 is controlled by an on/off switch 136 on the control panel 23 and such motor is attached to theupper plate 129 by fasteners 137.

In vorder to facilitate the tensioning and removal of the various belts the bearings 12% and 127 and the motor 135 may be mounted within slots which permit longitudinal movement in a well known manner. The pair of belts 117 disposed on each side of the head block 819 impart an equal driving force at both ends of the shaft 83 and the tensioning of such belts will restrict the rotational movement of such head block.

When the bark has been removed from the log it becomes necessary to remove the log from the bull wheels 14 to permit a new log to be placed thereon. In order to remove the debarked log, a log ejector mechanism is provided and includes a plurality of arms 14-h each having a concave end portion 141 which is normally disposed below the log 15 and intermediate of the bull wheels. The opposite ends of the arms 141] are attached to a shaft 142 journaled in pillow block bearings 143 fastened to the crossmembers 11 by bolts 14 1-. The arms 1419 are adapted to be swung through an arcuate path to raise the log from the bull wheels and to discharge such log from the side of the machine. This is accomplished by attaching one end of a rocker arm or link M5 to the shaft 142 and connecting the opposite end of such link by a pivot 146 to a yoke 14-7 fixed on the end of a piston rod 148 operated by an hydraulic cylinder 149. Fluid is introduced into and discharged from the cylinder 149 through fluid lines 15% and 151'and the flow of fluid to the cylinder is controlled by the operator from the control panel 23 through the medium of a lever 152 which controls a Valve 152. i

When the log has been raised from the bull wheels, such log will roll down the arms 1413 by gravity and will be discharged onto tapered plates or guides 153 disposed between rails 26 and 27 to permit the log to be discharged from the machine. When the arms 146) have discharged a log from the machine and are again lowered to their operative position, a new log to be debarked will be rolled from a higher elevation onto the bull wheels.

In order to prevent a log having a relatively large diameter from rolling completely out of the machine,

a safety stop 154 is mounted on the shaft 13 on the pin'153 which is disposedxbeneath the arm 14% in block 80. A multiple sheave pulley 123 is attached 1 to jack shaft 119 intermediate the bearings 12%) and substantially along the vertical center line of boom 49 and such pulley is driven by a series of belts 12 from a multiple sheave driving pulley 125.

The pulley 125 is fixed to a jack shaft 126 supported by bearings 127 fastened by bolts 128 to an upper plate such a manner that when the arm 14-0 is lowered into A counter balance weight 159 is attached to the hub 155 at the lower portion thereof so that when the arms raise thelog 15 over the bull wheels 14, the log willstrike arm 156 and pivot the same downwardly to permit the discharge of the log whereupon the weight 159 will return the arm 156 to an upright position so that when the arms 141) are again lowered they will contact pin 15%; and move the safety stopinto position. If desired an electro-mcchanical interlock may be provided between the carriage 28 and the log ejecting mechanism.

to prevent operation of the log-ejecting arms until the carriage has been moved to a position where it cannot be struck by the log. In the operation of a device, the boom to which the head block is attached normally is in an elevated position of approximately 40 to the horizontal when the cylinder.

machine is not in operation andthe slide plates 69 are normally'in their uppermost position due to the gas pressure within the cushion cylinder 73 acting against the piston on the piston rod 72. When a log to be debarked is placed on the bull wheels 14, lever 24 is operated to open valve 24' so that the fluid motor 22 will cause rotation of the bull wheels and consequently the Lever 44 then is operated in the desired direction to move the carriage 28 along the rails 26 and 27 until the boom 49 is disposed over the end of the log. Motor 135 is energized by the operation of switch 136 to cause rotation of the arbor 83 and holders 82 with the attached cutting knives S1. The slipper cylinders 97 then are operated by the appropriate up and down buttons 108 and 109 to position the leading slipper at an elevation above the trailing slipper substantially equal to the depth of the cambium layer of the log. Button G t-is then pressed to introduce fluid into elevating cylinder 58 through valve 58 and fluid line 62. This allows fluid at 1000 p.s.i. to be introduced into the top of the cylinder 58 and allows the fluid within the cylinder to be discharged into a reservoir. The speed of operation of this cylinder is controlled by a restricted orifice so that the full stroke of the cylinder requires approximately four seconds. The boom 49 is pivoted downwardly about the shaft 68 which will remain in its uppermost position until the leading slipper engages the bark of the log at which time the rotating knives will remove the bark from the end portion of the log and the trailing slipper is suspended outside of the limits thereof. Further downward movement of the elevating cylinder causes the cross shaft 68 and the slide plates 69 to move downwardly within the restraint of the guide members 70 and will cause the piston rod 72 to move downwardly within the cushion cylinders '73 againstthe pressure of the gas within such cylinder. When the piston rod 72 is moved downwardly a predetermined distance a limit switch will be actuated by the cross shaft which will open'the fluid circuit to the cylinder 73 and stop any further movement of the elevating Lever 44 will again be operated in the desired direction to move the carriage 23 along the rails 26 and 27 and move the boom, head block and cutters along the length of the log. While the cutters are traversing the length of the log the head block which is rotatably mounted on the boom will permit the knives and slippers automatically to align themselves to the surface being debarked. Any up and down variation in the surface of the log will cause up and down movement of the head block which will pivot the boom about the cross rod 55 and the fluid pressure within the cylinder 73 will compensate for such up and down movement While maintaining a substantially constant downward pressure on the slippers 87 and 88.

When the head block and the associated knives have traversed the full length of the log the button 63 will be pressed to introduce fluid into the bottom of the elevating cylinder and raise the boom to its inoperative position and the carriage 23 will be moved further along in the same direction past the limits of the log. The lever 152 will then be operated to raise the log ejector arms 140 which will lift the log over the bull wheels 14 and permit the log to gravitate downwardly of the arms 140 and be discharged from the machine. The lever 152 is then operated in a reverse direction to return the ejector arms 140 to their inoperative position and another log to be debarked is placed on the bull wheels. The operation of the carriage, boom and the slippers is then repeated in the reverse direction to remove the bark from the new log.

It will be obvious that the arrangement of the balanced boom, linkages, slides and cushion cylinder provides a novel means of obtaining any desired knife pressure on the log within close limits, of maintaining 3 V a constant pressure during the traversing of the log regardless of the variations of the log surface and of being able to repeat or change these conditions rapidly to obtain optimum knife pressure for various log species and conditions.

It will be obvious to those skilled in the art that various changes may be made in the invention without departing from the spirit and scope thereof and therefore the invention is not limited by that which is illustrated in the drawings and described in the specification, but only as indicated in the accompanying claims.

What is claimed is:

1. In a log debarker, log supporting mechanism, a reciprocable carriage connected to said log supporting mechanism, a floating boom having a cutter head on one end carried by said carriage, a compound lever system supporting said boom on said carriage and compressible fluid pressure means connected to and operable against the opposite end to exert and maintain a predetermined constant pressure on the cutter head against the work, said compound lever system including a lever having a fixed pivot carried by said carriage, a movable pivot spaced therefrom and an intermediate pivot, non-compressible fluid pressure means in contact with said intermediate pivot for swinging said lever, a link connecting the movable pivoted end of said lever with said boom generally centrally thereof whereby the boom will be elevated upon the upward swinging of the lever.

2. A log debarker comprising a base, log supporting and rotating mechanism on said base, a reciprocable carriage mounted for longitudinal movement along one side of said base, a floating beam mounted on a compound lever system pivotally carried by said carriage, said lever system being connected to said beam substantially midway thereof so that said beam is balanced about said connection, non-compressible fluid pressure means mounted directly on said carriage and connected to said lever system for raising and lowering said floating beam, a cutter head pivotally mounted on one end of said beam, a slidable pivot mounted on the opposite end of said beam, said slidable pivot being in communication with a compressible fluid pressure means connected directly to said carriage, said slidable pivot being normally in its uppermost position when the beam is raised and in the lowering and raising thereof but being displaced downwardly within said compressible fluid pressure means when said cutter head engages a log whereby a predetermined constant pressure will be exerted by the cutter head by the fluid pressure means.

3. Apparatus for removing bark from a log comprising a floating beam, a cutter head having a plurality of cutter blades mounted on one end of said floating beam, means carried by said floating beam for driving said cutter head and said blades, a carriage mounted for movement lengthwise of the log, spaced uprights carried by said carriage, at least one elevating beam pivotally mounted at one end on said uprights, non-compressible fluid cylinder means mounted on said carriage and connected to said elevating beam intermediate the ends of the same for rotating said elevating beam about said pivotal mounting, a fulcrum mounted on said floating beam generally centrally thereof,

' link means pivotally connecting the opposite endof said elevating beam with said fulcrum for rockably mounting said floating beam, a slidable pivot mounted adjacent the opposite end of said floating beam, compressible fluid cylinder means connected directly to said carriage and having a piston rod connected to said slidable pivot, whereby initial downward movement of said elevating earn by said non-compressible fluid cylinder means will lower said one end of said floating beam until said cutter head is in contact with the log and subsequent downward movement will lower the opposite end of said floating beam to compress the fluid in said compressible fluid cylinder means so that said floating beam is rockably mounted and a substantially constant pressure will be exerted on said cutter head.

4. Apparatus for removing bark from a log comprising a floating beam, a cutter head mounted on one end of said floating beam, a fulcrum mounted generally centrally of said floating beam, a carriage mounted for movement lengthwise of the log, a pivot carried by said carriage and being stationary relative thereto, an elevating beam mounted at one end on said carriage pivot and pivotally connected at the opposite end to said fulcrum, noncompressible fluid cylinder means carried by said carriage and pivotally connected to said elevating beam intermediate the ends thereof, compressible fluid cylinder means connected directly to said carriage and having a piston rod pivotally connected to said floating beam adjacent the opposite end thereof, whereby initial downward movement of said elevating beam will lower said one end of said floating beam until said cutter head is in contact with the log and continued downward movement of the elevating beam will lower the opposite end of said floating beam to compress the fluid in said compressible fluid cylinder means so that said floating beam is rockably mounted about said fulcrum and a substantially constant pressure will be exerted by said cutter head on the log.

5. The structure of claim 4 in which said cutter head includes a plurality of cutter blades, a depth penetrating gauge located beside said cutter head for controlling the References Cited by the Examiner UNITED STATES PATENTS 1,358,993 11/20 Shaw.

1,791,242 2/31 Himmelsbach et a1.

1,986,708 1/35 Bezner.

2,354,509 7/44 Dreher 5199 2,681,670 6/54 Prentice.

2,856,973 10/58 Horton 143-46 2,867,3 16 l/ 5 9 Uhlenkott.

2,925,106 2/60 Dillingham.

LESTER M. SWINGLE, Primary Examiner.

WILLIAM W. DYER, JR., Examiner. 

1. IN A LOG DEBARKER, LOG SUPPORTING MECHANISM, A RECIPROCABLE CARRIAGE CONNECTED TO SAID LOG SUPPORTING MECHANISM, A FLOATING BOOM HAVING A CUTTER HEAD ON ONE END CARRIED BY SAID CARRIAGE, A COMPOUND LEVER SYSTEM SUPPORTING SAID BOOM ON SAID CARRIAGE AND COMPRESSIBLE FLUID PRESSUE MEANS CONNECTED TO AND OPERABLE AGAINST THE OPPOSITE END TO EXERT AND MAINTAIN A PREDETERMINED CONSTANT PRESSURE ON THE CUTTER HEAD AGAINST THE WORK, SAID COMPOUND LEVER SYSTEM INCLUDING A LEVER HAVING A FIXED PIVOT CARRIED BY SAID CARIAGE, A MOVABLE PIVOT SPACED THEREFROM AND AN INTERMEDIATE PIVOT, NON-COMPRESSIBLE FLUID PRESSURE MEANS IN CONTACT WITH SAID INTERMEDIATE PIVOT FOR SWINGING SAID LEVER, A LINK CONNECTING THE MOVABLE PIVOTED END OF SAID LEVER WITH SAID BOOM GENERALLY CENTRALLY THEREOF WHEREBY THE BOOM WILL BE ELEVATED UPON THE UPWARD SWINGING OF THE LEVER. 